Biological and Applied Environmental Research, 2017 Volume 1, Number 1, 69-87 Influence of Environmental Variables and Different Hosting Substrates on Diatom Assemblages in the Shatt Al-Arab River, Southern Iraq MAITHAM A. AL-SHAHEEN1 & ADIL Y. AL-HANDAL2* 1Department of Ecology, College of Science, University of Basrah, Iraq 2* Department of Biological and Environmental Sciences, Gothenburg University, Sweden *Corresponding author: [email protected] Abstract: The relationship between diatom species, environmental variables and different substrates in Shatt Al-Arab river was studied during the period from December 2012 to November 2013 in seven stations along the course of the Shatt Al- Arab river. A total of 193 taxa belonging to 70 genera were identified. Diatom assemblages in the Shatt Al-Arab river included freshwater forms (28%), brackish water forms (11%) and marine forms (34%). The results of multivariate analysis (PCA) showed four components, the first included most of species which are further divided into two groups, the first group encompassed marine species with strong correlation with turbidity, alkalinity, EC and salinity, whereas the second group included species which have strong correlation with nutrients. Both PCA and CCA analysis showed most of the diatom species having strong correlation with plankton and plant host substrates, but few species preferred the mud and solid substrates. Keywords: Diatoms, environmental variables, substrates, Shatt Al-Arab river. INTRODUCTION Diatoms are one of the most important groups of microalgae in the freshwater environment. They serve as potential bioindicators for water quality (Harding et al., 2005; Leelahakriengkrai & Peerapornpisal, 2010; Bere, 2014). The diatoms have been widely used to infer past limnological and oceanographical conditions. Based on their variable ecological preferences, they were successfully used to monitor different marine and freshwater aquatic systems, including several aspects like hydrologic and climatic changes in saline lakes, acidity of surface water, lake eutrophication, long-term environmental changes, water level change in freshwater lakes, coastal paleoenvironment indicators and relative sea level changes, environmental changes in brackish waters, estuaries and shallow coastal, marine paleoceanography, environmental changes at both Arctic and Antarctic regions, in addition to other applications like forensic science, archeology, exploration of oil and gas in different regions and atmospheric transport markers (Smol & Stoermer, 2010). Every species of diatoms requires different kinds of physical, chemical and structural features for its habitat. When these features are subject to minor changes due to natural or human activities, correlated diatom communities respond quickly and mostly change in both biomass and taxonomic structure (Lavoie et al., 2008; Bere & Tundisi, 2009). Most pollution monitoring programs in freshwater ecosystems include routine checking of diatoms water ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ Received: May 8, 2016, accepted: Jul. 14, 2016 70 Al-Shaheen & Al-Handal quality indicators (Taylor et al. 2007c; Lavoie et al. 2008; Bere & Tundisi, 2011). In Many developing countries, diatom based monitoring programs are applied using diatom indices modeled in European or other western ecosystems which might not be applicable accurately in these countries (Pipp, 2002; Bere et al., 2014). Such situation calls for investigations to find diatom models suitable for each environment, e.g. in tropical and subtropical regions. Investigations on using diatoms as bioindicators to assess water quality in aquatic ecosystems of Iraq are rather rare. The study of diatoms in relation to their tolerance to organic pollution (saprobity) has been pioneered by Al- Handal & Abdullah (1994). Eassa (2012) may have been the first to use diatoms indices for the assessment of water quality in Shatt al-Arab river, followed by Al-Saboonchi et al. (2012) who applied P-IBI for the assessment of water quality at Chebaish marsh. Recently, Al-Ankush (2013) carried out a study to monitor Shatt Al-Arab river’s water quality by models prepared for benthic diatom assemblages. The present study is aiming at investigating the relation of diatoms distribution to changes in aquatic parameters, both physical and chemical and also to explore the relationship between diatom assemblages and the different natural substrates inhabited by diatoms taxa using direct observations and statistical analysis. MATERIALS AND METHODS Study area Seven stations were selected along the course of Shatt Al-Arab river (Fig. 1). Station 1 (Al-Mohamadiyah, N: 30 36.623, E: 47 45.662) lies about 14 km north of Basrah city center. Samples were collected from the eastern bank of this site which is muddy and supports dense growth of some aquatic plants such as Phragmites australis (Cav.) Trib. Ex Steud., Typha domingensis Pres. and Schoenoplectus litoralis (Schrad) Palla. Station 2 is located at Al-Maqal area (N: 30 33.755, E: 47 47.563), south of Al- Sendibad island, opposite to Al-Maqal port. Sampling was carried out in the eastern muddy bank which was covered by many species of aquatic plants, the most common of these were Phragmites australis, Typha domingensis, Schoenoplectus litoralis, Ceratophyllum demersum, Myriophyllum spicotum, Potamogeton crispus, Potamogeton perfolitus and Vallisneria spiralis. Influence of environment variables on diatoms 71 Figure 1: Map showing location of study sites at Shatt Al-Arab river. Station 3 is located at Al-Bradhiyah village (N: 30 30.376, E: 47 51.328), opposite to a drinking water treatment plant, at the southern part of Basrah city center. Samples were obtained from the western bank which was sandy to muddy with few aquatic plants such as Phragmites australis, Ceratophyllum demersum and Vallisneria spiralis. Station 4 was at Mehellah village (N: 30 28.476, E: 47 55.343), Abu Al-Khaseeb district, in front of a drinking water treatment plant. Samples were taken from the western bank. Sediments were mostly muddy with some macrophytes prevailing such as Phragmites australis, Ceratophyllum demersum, Vallisneria spiralis and Schoenoplectus litoralis. Station 5 was at Abu Flous village (N: 30 27.251, E: 48 02.810). Both banks of the river were muddy with few macrophytes and less human activities. In some parts of the western narrow tidal flat, sand and cobbles cover the sediment which is remnants of old military constructions. Few macrophytes can be seen such as Schoenoplectus litoralis, Ceratophyllum demersum and Vallisneria spiralis. Station 6 was at Al-Seebah village (N: 30 20.240, E: 48 16.145). The region suffers sever pollution coming from Abadan oil refinery which lies on the eastern bank. Turbidity increases considerably when Karun river (20 km to the north) discharges. Sea water front reaches this station during high tide. Samples were obtained from the western side which was muddy with only two macrophytes growings, Cyperus laevigatus and Enteromorpha sp. 72 Al-Shaheen & Al-Handal . Station 7 was at Al-Faw town (N: 29 59.240, E: 48 27.360), in front of small oil port. Sea water effect was very clear. Karun river discharge reaches the station during low tide. Tidal flat expands to 50 m during low tide and sediments were almost silty. Aquatic macrophytes disappear except for scattered Enteromorpha sp. but the salt tolerant plant Salicornia herbacea was widely distributed. Samples collection Samples for various analyses were collected monthly from December 2012 to November 2013 during lower level of low tide from all stations. Sampling from stations 1, 2, 3, 4 and 5 were collected on the same day starting from station 5 up to station 1, while samples from the rest of stations (6 and 7) were obtained on another day of the same week. Tides period was estimated using a Tidal Prediction Program (Total Tide) version 1,0,11,0 (United Kingdom Hydrographic Office, UK). Sampling and measurements of environmental parameters For chemical analysis, water samples were collected approximately from the middle of the river by immersing and filling a 2 L polyethylene bottles from15-30 cm depth. All samples were kept in a cool box. Analyses were done immediately upon return to laboratory. For dissolved oxygen determination, Winkler bottles were filled with water and fixed directly by adding 2 ml of each of manganese sulfate solution, alkaline iodide azid solution and concentrated sulfuric acid and then analysis was completed in the laboratory. Some physical and chemical parameters were measured in situ. These included air and water temperatures, light transparency, salinity, electrical conductivity, turbidity and hydrogen ion concentration (pH) using different instruments. Reactive Nitrite (NO2), nitrate (NO3), reactive phosphate (PO4) and reactive silicate (SiO3) were measured according to Strickland & Parson (1972), Lind (1979) and APHA (1999, 2005). Diatoms sampling, cleaning and slides preparation Planktonic diatoms at all stations were collected monthly using Wildco Phytoplankton net with 20 µm mesh size, 20 cm mouth diameter and 90 cm long (Wildco Supply Company, USA).The net was hauled behind a motor boat running at its lowest speed for 15 minutes. Samples were kept in plastic bottles, marked and fixed by adding 4% formalin. Benthic diatoms were also collected monthly following the methods described by Kelly